The present application is the national stage under 35 U.S.C. 371 of PCT/DE99/01244, filed Apr. 24, 1999.
The invention relates to an injection device with a syringe, in particular a disposable syringe, for injecting an injection fluid under the skin.
Carrying out medically appropriate injections by means of a syringe presupposes a minimum degree of medical knowledge and practical skill. Adherence to these requirements is usually guaranteed in the stationary hospital or care sector, since, here, syringes are handled by medically trained specialized personnel; however, with the increase in chronic illnesses due to the increasing life expectancy of the population, the domestic care sector is also increasing.
The result of this is that the handling of syringes must increasingly be capable of being carried out by the medical lay public as patients for the purpose of self-treatment at home; apart from a certain threshold of inhibition when a syringe is applied, adherence to the above-mentioned criteria is also no longer guaranteed as the age of the patient increases, for example because of motor disturbances or impaired vision. This has increasingly led, in recent decades, to the design of injection devices which operate partially or completely automatically and into which, in particular, conventional ready-made syringes can be inserted, so that it only remains for the patient to position the front end of this injection device on the place of injection and then actuate a trigger means in the injection device, in particular by finger pressure, whereupon the pricking of the needle and the injection of the injection fluid are then carried out mostly under the effect of a spring means. Examples of such injection devices are shown in DE 29 50 140 C2, DE 14 91 842 C2, DE 24 36 000 C2, EP 0, 144,625 B1, EP 0, 516,473 B1 and EP 0, 577,448 A1.
The invention proceeds from a generic device, such as is described by FR 2 733 155 A. This injection device contains built-in parts which are held in the housing and which, under the action of a spring as drive means, load the syringe in such a way that, as a result of a successive linear displacement of the syringe and of the injection needle in the housing, first the introduction of the injection needle of the syringe under the skin takes place and only thereafter is the injection fluid injected. After injection has taken place, these structural parts are then returned to their initial position again as a result of an opposite movement. Within this cycle of movement, it is necessary to extract the emptied disposable syringe from the injection device and replace it by a filled, new disposable syringe, so that the injection operation can then be restarted anew.
To that end, the housing has an axially displaceable control sleeve, which after the return of the built-in parts that effect the linear displacement is drawn into an opening position, whereupon a new disposable syringe can be put in place and the control sleeve can be thrust into a closing and operating position. The tension of the spring that effects the injection stroke is generated here upon retraction of the control sleeve, until a locking position is reached, to which end the spring force to be overcome must be fully brought to bear by the patient to its full extent as a tensile or compressive force. The execution of one complete injection cycle in this design requires a plurality of a successive handling actions in a fixed order.
U.S. Pat. No. 5,137,516 A shows an actuation unit and a housing unit for receiving the syringe, which for actuating the syringe must be placed against one another in axially aligned fashion and joined together. To that end, a screw sleeve is provided which is a component of the housing unit, and onto which the actuation unit can be screwed once a filled syringe has been put in place, and from which the actuation unit has to be unscrewed again after the injection has been made, so that the empty syringe can be removed.
German Utility Model DE 89 12 091 U shows an injection device operating in a single stage, in which the piercing of the skin and the injection proceed simultaneously. As in the aforementioned U.S. Pat. No. 5,137,516, an actuation unit and a housing unit for receiving the syringe are provided, but they are disposed fixedly parallel to one another and thus form a structural unit. A xe2x80x9ccolumnxe2x80x9d is axially guided in the actuating unit and has a plate on its upper end that by rotation of the column either blocks or releases the insertion opening of the housing unit, thus defining a closing and operating position and an opening position relative to the housing unit.
The handling of both these last two injection devices when the disposable syringe is being changed requires, particularly when the two housing parts, together with the reinserted, new ready-made syringe, are brought together accurately in terms of fit and direction, some degree of manual skill which cannot be presupposed in the group, referred to above, of chronically sick, older people; this previously known solution is therefore somewhat unsuitable for this group in particular.
The essential object of the invention is to develop generic injection devices in such a way that, whilst having a simple mechanical design, the patient""s actions required for handling are reduced to a minimum, in particular the extraction and insertion of the disposable syringe are simplified to such an extent that only minimal requirements are demanded of the (remaining) physical and mental abilities of the patient.
This object is achieved, according to the invention, in conformity with the defining part of patent claim 1.
The essential idea of the solution according to the invention is to combine a multiplicity of drive, control and safety functions in a central structural part, the control sleeve, which manually is extremely easy to handle, since it needs merely to be rotated relative to the housing:
The control sleeve is part of the housing inasmuch as it serves, instead of, for example, a flap, for closing and for opening the interior of the housing, in which the ready-made syringe is held.
The control sleeve is part of the drive means insofar as, when the housing is being opened by the rotation of the control sleeve, a counterstroke of the slide and tappet is generated counter to the action of a spring executing the injection strokes, said counterstroke conveying these two structural parts into their original locking position again, separate measures and actions not being required for this absolutely necessary sequence.
The control sleeve is also a control means insofar as, depending on its position, it blocks the trigger means of the injection device or permits its activation.
The control sleeve also makes it possible to have further advantageous embodiments of the solution according to the invention for increasing the operating safety and handling convenience, insofar as it directly actuates an ejection means which, after injection has taken place, automatically presses the empty ready-made syringe toward the patient, when the housing is opened, by means of the control sleeve, and thus makes extraction easier, and said control sleeve is also utilized for feedback of the position and operating state of the injection device, said feedback being capable of being easily detected by the patient""s senses.
Other advantageous embodiments according to the invention relate to a clearly detectable, acoustic signal means, by which the end of an injection operation is indicated to the patient.
This diversity of functions can be implemented by means of a simple design of the injection device; thus, the essential structural parts of the injection device can, for example, take the form of injection moldings which can easily be mounted, so that the injection device can be produced cost-effectively in terms of material and labor.